A bit of clarity is required.
When you are issued a ATPL, CPL or PPL, you are issued a licence. That's all. What you can do with that licence is denoted by the ratings that you hold.
Most PPL's only hold a Single Engine Piston rating. Hence all they are allowed to fly is single engine pistons. This by the way, is valid for two years and there are various ways and means to revalidate/renew this rating.
The actual PPL licence is valid for 5 years. To renew this you send a nice fee to the CAA and your licence is renewed for another 5 years. This is the same for a CPL and ATPL (unfrozen).
An ATPL(f) is a common term for a CPL ME/IR with an MCC. So,
1) You have a CPL, this is renewed every 5 years by sending a fee to the CAA
2) You have a Multi Engine Piston rating. This is renewed every year, normally by a test with an examiner.
3) You also have an IR. Again this is renewed every year. This can be done in a sim or in an actual aircraft. As it's a multi engine IR, you will need to complete this in a multi engine scenario.
4) MCC does not expire.
So, to clarify further. To keep all your ratings valid, you need to be tested every year. To keep your CPL valid, you need to send the CAA some money every 5 years.
And no, renewing your IR in a sim will NOT renew your Multi Engine Piston rating.
As to how much it costs, I suggest you contact some schools in your area for some prices.